The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A typical vehicular engine, which is an internal-combustion engine, is provided with an exhaust system for the discharge of exhaust gas generated by burning fuel in a cylinder.
A cylinder head is provided therein with an exhaust port so as to allow exhaust gas in the cylinder to be discharged through the exhaust port. The exhaust gas discharged from the exhaust port is supplied to a catalytic converter through an exhaust manifold and an exhaust pipe.
Recently, in order to reduce exhaust interference, an exhaust pipe is elongated so as to have a sufficient length. However, this construction increases the light-off time (LOT), which is taken to reach the activation temperature of a catalyst in order to purify exhaust gas when an engine is started up at a low temperature, thereby degrading the capability of satisfying the exhaust gas emission standard. Furthermore, a measure of increasing the content of noble metals contained in the catalytic converter in order to improve the capability causes excessive increase in manufacturing costs.